Structure of Airblast Sprays Under High Ambient Pressure Conditions

Zheng, Qing-ping; Jasuja, A. K.; Lefebvre, A. H.

doi:10.1115/1.2817014

Cited by 28 publications

(14 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Two types of counter-rotating double-swirl airblast atomizers (for example, see Ref. [17]) were used, designated as U4D4 and U8. As for U4D4 type, liquid fuel (kerosene) is injected through four injection holes upstream and an annular exit at its atomizer lip.…”

Section: Methodsmentioning

confidence: 99%

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

Matsuura

Uesaka

Iwasaki

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

View full text Add to dashboard Cite

The visualization of the pilot flame of a coaxially-staged aero-engine lean-burn fuel injector, not only downstream but also inside of the pilot nozzle, was successfully performed at realistic aero-engine conditions. Optical access toward the inside of the nozzle was achieved through the inner and outer shrouds, both of which were made of transparent quartz. The image distortion caused by complex contours of the two shrouds was corrected by a method based on optical ray tracing, which realized precise determination of spatial intensity distribution of optical signals. Line-of-sight OH chemiluminescence, cross-sectional OH-LIF, kerosene LIF and kerosene Mie scattering were employed as diagnostic tools. The effects of pilot local air-to-fuel ratio on spray flame structure were revealed, both inside and downstream of the pilot nozzle under stable combustions. As the pilot mixture got rich, the main reaction zone moved from inside of the pilot nozzle to the region near the injector lip downstream of the injector exit. The OH-LIF signal was detected near the central axis surrounded by the fuel spray. It was also observed near the back-step of the pilot nozzle for the rich cases. The experiments under combustion oscillation were also conducted and the correlation of phenomena inside and downstream of the pilot nozzle was captured. It was clarified that the reaction enhancement in the outer part of the lip vortex region was caused by the convection of rich mixture, which appeared near the pilot atomizer lip at 150~210deg earlier oscillation phase angle. KeywordsAero-engine combustor, Optical burner/injector, Staged lean-burn injector, Laser induced fluorescence, Ray tracing, Optical refraction correction, Elevated temperature and pressure IntroductionFor reduction of NOx from aircrafts, coaxial-staging lean burn fuel injection systems have been studied intensively these days [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and some of them have been already in service. Typically, they consist of a non-premixedmode pilot nozzle at the center for flame stability and a lean premixed-mode main nozzle surrounding the pilot for drastic NOx reductions. For such an injector, both fuel injection and fuel/air mixing start a few centimeter upstream from the injector exit (i.e. entrance of the combustion chamber). Moreover, this is also true for its pilot flame. Therefore, many important phenomena take place in regions enclosed by the metal walls of the injector, where the application of optical diagnostics is not straightforward compared with a conventional combustor. In our previous work, visualization of fuel spray/vapor behavior and fuel/air mixing inside the main nozzle (i.e. the premixing duct) was performed by high speed visualization and/or LIF techniques [10,11,15]. Through a fullycontoured quartz-made transparent outer-shroud, dynamic motion of fuel sprays under combustion oscillations at an elevated pressure and temperature was clearly captured and discussed in relation to the flame dynamics downstream [15]. ...

show abstract

Section: Methodsmentioning

confidence: 99%

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

Matsuura

Uesaka

Iwasaki

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

View full text Add to dashboard Cite

show abstract

“…In many of the previous investigations [5][6][7][8][9], the effect of ambient pressure (P3) is investigated keeping the air to liquid ratio (ALR) constant, but the air and liquid flow rates are proportionately increased with respect to the change in P3. Even though this represents a typical engine flow scenario, individual effects of ambient conditions need to be investigated.…”

Section: Test Conditionsmentioning

confidence: 99%

“…The effect of ambient pressure and temperature on the spray structure of the pressure swirl and airblast sprays has been investigated in several previous studies [5][6][7][8][9][10][11][12]. In most of these investigations, the external spray structure and drop size variation are captured at various operating conditions.…”

Section: Introductionmentioning

confidence: 99%

Effect of Ambient Pressure on the Internal Atomization Processes of a Gas-Turbine Fuel Injector

Shanmugadas

Chakravarthy

2021

ICLASS

View full text Add to dashboard Cite

The present work investigates the internal atomization characteristics of a gas-turbine fuel injector under elevated ambient pressure conditions. The injector is a piloted prefilming type airblast atomizer in which a dual orifice nozzle is used as the pilot nozzle. The injector assembly involves primary and secondary swirlers which are separated by a curved prefilmer called venturi. The fuel placement and droplet size at the injector exit depends on the flow evolution within the atomizer geometry which is influenced by the individual hardware components and ambient conditions. The injector geometry is split into different modules such as pilot nozzle, primary swirler, venturi, secondary swirler etc. and the modules are combined together forming different stages such that spray formation can be tracked as the flow evolves through it. High-speed imaging and laser induced fluorescence (planar and volumetric) imaging are performed to capture the internal flow field and phase Doppler interferometry measurements are conducted to obtain droplet size and axial velocity variation at every stage. Experiments are conducted up to 7 bar ambient pressure at constant fuel air ratio (FAR) with each stage configurations. The increase in ambient pressure lead to the collapse of the primary spray from the dual orifice nozzle which resulted in a narrow cone angle and in the formation of bigger droplets. Further, the ambient pressure influenced the wall filming process forming thick liquid films and rims at the prefilmer tip. The counter-rotating shear layer formed at the secondary swirler exit limited the influence of ambient pressure at the secondary exit and overall, the average droplet size increased at the injector exit. The effect of spray cone collapse of the pilot nozzle spray is not visible at the injector exit. This suggests that the wall filming on the venturi surface and the shear layers at the secondary exit, are the major contributing parameters in the drop formation and fuel placement at the injector exit at elevated pressure operating conditions.

show abstract

“…Physical property of kerosene was referred from the article [19]. When the temperature of pure water is changed from 283 to 323 K, liquid viscosity µ L becomes less than half of the original value.…”

Section: Experimental Setup and Conditionmentioning

confidence: 99%

Longitudinal oscillation of a liquid sheet by parallel air flows

Oshima

Sou

2019

International Journal of Multiphase Flow

View full text Add to dashboard Cite

A liquid fuel sheet injected into the combustor of gas turbine engines is deformed and atomized by the complex interactions between the liquid sheet and air flows. Aiming at improving the control technology of a fuel spray, the oscillation phenomenon and the primary break-up process of a planar liquid sheet with air flows have been studied for many years. Based on the previous studies, we propose a new correlation on the longitudinal wavelength λ Lon given by λ = � and that on the oscillation frequency f Lon of a liquid sheet given by f = ′ � / � , where MR Lip is the lip momentum ratio defined in this study. In addition to previous visualization experiments of a planar liquid sheet and parallel air flows with various densities of gas and liquid, gas and liquid velocities, liquid sheet thicknesses and lip thicknesses, we carry out an additional experiment with various gas velocities and liquid viscosities to cover all the effects of fluid properties, injector geometries including gas and liquid boundary layers on the deformation and the atomization characteristics of the oscillating liquid sheet. Image analysis is conducted to obtain f Lon . As a result, we confirm that liquid viscosity does not affect f Lon and λ Lon of the liquid sheet in a wide range of liquid Reynolds number. Finally, we verify the validity of the correlations of λ Lon whose constant c is 14.3 and f Lon whose constant c' is 0.095.

show abstract

Structure of Airblast Sprays Under High Ambient Pressure Conditions

Cited by 28 publications

References 14 publications

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

Effect of Ambient Pressure on the Internal Atomization Processes of a Gas-Turbine Fuel Injector

Longitudinal oscillation of a liquid sheet by parallel air flows

Contact Info

Product

Resources

About